Modal metaphysics and the priority of causes in Hume's Treatise

At the start of his discussion of causation, Hume claims to demonstrate that simultaneous causation is absolutely impossible; all causes must precede their effects in time. I argue that considering Hume’s modal theory can reveal two important and previously unaddressed features of this argument. First, his modal metaphysics resolves one of the most pressing extant interpretive issues: how Hume is able to infer from the claim that it is possible for some object to be simultaneously caused to the claim that it is possible for all objects to be simultaneously caused. This inference, I argue, is justified by Hume’s combinatorial modal theory for relations. Second, his distinction between absolute and natural modality raises a problem that has not yet been identified in the literature. Hume is trying to conclude that something is metaphysically impossible, but one of his premises relies on a mere natural impossibility (that no object can begin to exist uncaused). This, I argue, is an intractable problem: Hume cannot get the conclusion he wants because it depends on an equivocation between two strengths of modality